The present invention relates to the use of an optical sensor for identifying marks on a printer print ribbon, or transfer ribbon. The sensor provides a reliable and accurate signal indicating that particular marks on the ribbon have been sensed using low cost light sources and optical sensors.
In the prior art, various ribbons have been advanced that have marks for identification of separations between individual blocks or segments of different colors, and also for identifying positions of a ribbon that is being used in a printing operation or a lamination operation on a printed card. The web or ribbon may carry lamination xe2x80x9cchipsxe2x80x9d which are positioned precisely for laminating onto a printed card, and then removed from the web or ribbon when they are laminated in place.
Additionally, separate identification marks can be placed onto the ribbon for identifying particular panels or longitudinal positions of the ribbon. It is necessary to make the identification of the marks rapidly, and very precisely when the sensed object is used. It has been found that using standard reflective optical sensors can cause unwanted reflection of LED light on shiny surfaces that will make it hard to distinguish between a shiny printer ribbon surface, and a mark on such ribbon that is to be used for identification of a particular position.
The present invention relates to the use of a reflective type optical sensor for identifying individual marks that have been placed onto a shiny or reflective surface to identify particular locations on the surface. The positions or locations on a ribbon needing identification might be lines between different color sources of a thermal dye sublimation or a thermal transfer ribbon or web, may be the position of a block to be printed on an intermediate transfer ribbon. Additionally, marks can be used for identifying the position of lamination chips that are to be laminated onto previously printed identification cards and are carried on a web.
The LED that is used can be used without focusing lenses. Angling the axis of a light beam so that it is not perpendicular to the plane of the shiny ribbon surface has been found to increase the sensitivity of the sensor, and decrease incidents of the reflective, near mirror like surface, causing an output from the light sensitive sensor.
A number of sensor assemblies, each with a light source in the assembly can be used across the width of a printer ribbon, for sensing a number of different types of marks, but in each instance the sensor assembly is positioned so that the light source axis is at an angle relative to the plane of the ribbon other than perpendicular or near perpendicular and the light sensitive sensor is positioned along the ribbon in a location to minimize the amount of reflected light from shiny surfaces or mirror like surfaces of ribbon and yet provide a position signal from light that is reflected in a diffused manner from an identification mark. The identification mark can be a white mark or a light mark that may be off color white, including yellows. The diffusion of reflected light is needed, and white is a preferred color.
The sensor body is inclined at a selected angle so the light axis is preferably between 30 and 45xc2x0 relative to the plane of the surface being sensed, such as the surface of a web or ribbon in a printer.
The light that is diffused by the white mark and reflected back to the sensor is from light beams that are not reflected directly back from a shiny surface. The shiny ribbon surface acts more like a mirror and reflects light at an angle of reflection that is substantially equal to the angle of incidence.